1. Field of the Invention
The present invention pertains to the field of oxinates and, particularly, to the therapeutic use of chelated metal 8-hydroxyquinolinates in the treatment of cancers, precancerous lesions, and other abnormal tissues.
2. Statement of the Problem
A preferred treatment modality for many cancers is surgical excision of the cancerous lesion. Surgical excision is not always desirable when surgery could sever nerves or produce scars that interfere with normal movements in tissues proximate the site of surgery.
Chemicals have been developed to treat cancers. Rate-sensitive cytotoxic drugs have cytotoxic effects on all tissue types, but are particularly effective against certain cancers that function at a metabolic rate greater than the metabolic rate of normal cells. The increased metabolic rate of these cancers makes them more susceptible to the cytotoxicity of the drugs. In this manner it is possible to provide a dosage that is fatal to cancer cells, while that same dosage is not fatal to normal cells. By way of example, U.S. Pat. No. 5,684,169 teaches the formation of cyclodextrin complexes of taxol to improve the solubility of taxol in water. Taxol is a cytotoxic drug that is believed to attack and kill cancer cells with a rate-sensitive effect.
Other chemicals are specifically designed for the treatment of skin cancers and cancers that reside close to the skin. U.S. Pat. No. 5,605,700 describes a transdermal preparation containing toremifene for use in treating cancers of the skin or cancers that reside a short distance from the skin, such as metastic lesions of breast cancer. The transdermal preparations are said to be of particular interest in the treatment of melanoma, lymphoma, Kaposi's sarcoma, and fungoides mycosis. Escharotics or caustic chemicals, such as Podophylin or tricholoroacetic acid which are used in the treatment of skin cancer, venereal warts and human papilloma virus, are designed to produce a chemical burn that destroys substantially all of the tissues in contact with the chemical. None of these chemicals is selective in destroying only the lesion while leaving behind healthy tissues that exist close to the site of the lesion, i.e., the chemicals lack selectivity and specificity.
The chemical 8-hydroxyquinoline is not used for the treatment of epithelial lesions, such as epitheliomas and venereal warts. 8-hydroxyquinoline is known by various other names including oxine, 8-hydroxy-chinolin, hydroxybenzopyridine, and 8-oxyquiniline. The federal government has approved 8-hydroxyquinoline for cosmetic use in low concentrations of less than five percent. At these concentrations, 8-hydroxyquinoline functions as a cosmetic biocide, as reported in JACT 11(4), 1992. U.S. Pat. No. 4,302,467 reports the use of 8-hydroxyquinoline or its chelates in combination with dehydroacetic acid or sorbic acid. The combination is reported to work synergistically against bacteria and fungus. According to the Merck Index 11th Edition, Merck & Co. publ., p. 4779. (1989), 8-hydroxyquinoline is used as a fungistat, a chelating agent in the determination of trace metals, and a disinfectant.
Chapter ten of the book Albert, Selective Toxicity 3rd Ed., New York, John Wiley & Sons, Inc. (1965) states on page 370-378 that the antibacterial action of oxine is due to chelation. Iron-chelated forms of oxine are toxic to gram-positive bacteria when mixed with Fe3+ at a 1:1 molar ratio and a 1:2 molar ratio of oxine to iron, but toxicity diminishes at a 1:3 ratio. Despite its strong antibacteriological effects, oxine and its derivatives are not normally injected into the bloodstream because they are inactivated by red blood cells, which secrete a substance that binds oxine.
There remains a need for a topically applied therapeutic composition with selective toxicity in the treatment of epithelial lesions.